As it is well known in the art, the helmets which are used during sporting activities generally utilize a construction based on three primary components: an exterior shell, an impact absorbing liner and a comfort liner.
The exterior shell, made of a rigid material, for example a thermoplastic polymer like polycarbonate or a fiber-reinforced polymer, has the function to protect the head of the helmet's wearer against impacts with the ground or other objects.
The exterior shell is also suitable for dissipating, at least partially, in case of an accident, the impact forces acting on the helmet by spreading and transferring them to the second component of the helmet, the impact absorbing liner.
The impact absorbing liner is positioned adjacent to the exterior shell and it is shaped so as to correspond to the shape of the wearer's head.
The function of the impact absorbing liner is to absorb the impact forces which are generated during an accident, thereby preserving the wearer's head.
Generally, the impact absorbing liner is made of relatively rigid material, like expanded polystyrene.
The third component is the comfort liner which resides on the surface of the impact absorbing liner facing the wearer's head.
The comfort liner is usually made of a combination of soft foam and fabric materials and has the function to make comfortable the wear of the helmet, by avoiding that the wearer's head gets in direct contact with the rigid impact absorbing liner.
It is also known that a helmet, in order to accomplish in the best way its protection function, needs to be stable and secure on the wearer's head. Such occurrence is possible only when the impact absorbing liner is very close in shape and size to that of the wearer's head. In this case, the comfort liner can be soft and comfortable without affecting the stability of the helmet since it has the support of the rigid impact liner placed beside it.
Nevertheless, considering the variety of sizes and shapes of the heads of the world population, it is quite difficult that a helmet which fits properly on the head of one person, could fit in a stable and secure manner on the head of a another person.
To achieve such result, most helmet manufacturers offer to their customers, even if it is expensive and difficult to do, the opportunity to choose between different sizes and shapes of helmet, in order to increase the possibility that the customer could find a helmet which is stable and secure on its head and at the same time comfortable.
In the name of the same applicant an International Patent Application has been filed (published as WO2010122586) which discloses a new and innovative impact absorbing liner suitable for being used as part of a helmet. Such impact absorbing liner comprises adjustable means which allow to easily change the interior size and shape of the impact absorbing liner. In a preferred embodiment the adjustable means of the impact absorbing liner comprises a plurality of displaceable blocks, positioned in the area of the impact absorbing liner facing the temples, the ears and the occipital bone of the wearer of the helmet. By moving towards or away from the wearer's head the displaceable blocks, it is possible for the wearer to adjust the shape and size of the internal comfort liner according to his/her needs. Such impact absorbing liner allows to solve the drawbacks above mentioned, making a helmet stable and secure over a plurality of different heads.
Nevertheless, it should be noted that even if the head of the user fits properly inside the impact absorbing liner of the helmet, further problems can still arise.
As a matter of fact, also for users having an head with a given proportion, the location of the eyes, ears and face is not constant and varies independently from the size of the head.
The result is that on many users the helmet sits too low on the face. This occurrence can cause unnecessary pressure on the eyebrows of the user and can potentially reduce the field of view, by affecting in this way the safety of the user.
Furthermore, many user may have a head with a given proportion but different top profile. In this case, the shape of the impact absorbing liner and comfort liner, not matching the specific shape of the head, may cause the helmet to sit on the user head at an unusual or uncomfortable angle.
Also this occurrence can lead to some problems. As a matter of fact, some areas of the helmet can exert an unnecessary pressure on the head. Moreover, also in this case, the field of view of the user can be reduced.
Some helmets are provided with one or more pads suitable for being attached by Velcro® means over the top internal surface of the impact absorbing liner.
Nevertheless, the provision of such pads does not solve the above mentioned problems.
As a matter of fact, for being efficacious and for helping the user to adjust the positioning of the helmet over its head, the pads must have different thickness and must be able to be swapped out for one and other.
In view of the above notes, for assuring a proper fitting of the helmet over the user's head, every helmet should be supplied with at least one set of pads having different thickness. Such eventuality would imply an increase of the costs and an useless consumption of material. As a matter of fact, multiple pad thickness would need to be supplied with every helmet, but only one thickness would ever be worn.